In recent years, the functionality of portable electronic devices such as mobile phones, personal computers (PCs), and PDAs (Personal Digital Assistants) is significantly advancing, and portable electronic devices equipped with a camera module and thus having an imaging function are commonly available. In such portable electronic devices, a lens in the camera module is moved in an optical axis direction to achieve focusing and zooming.
A general conventional method for moving the lens within the camera module is to use a voice coil motor or a stepping motor as a driving unit. Recently, from the viewpoint of miniaturization, a camera module using a prescribed actuator element as a driving unit has been developed. Examples of such an actuator element may include a polymer actuator element. The polymer actuator element includes, for example, a pair of electrode layers and an ion conductive macromolecular layer (hereinafter referred to simply as a macromolecular layer) held between the electrode layers. The macromolecular layer contains, for example, water, an ionic liquid, or a high-boiling point organic solvent. In such a polymer actuator element, when an electric field is applied between the pair of electrode layers, ions in the macromolecular layer migrate, and displacement thereby occurs. Therefore, the operating characteristic of the polymer actuator element such as the amount of displacement and the speed of response depend largely on the environment of ionic conduction. The polymer element is used as the polymer actuator element, as described above, and is used also as a polymer sensor element, an electric double layer capacitor, a secondary battery, etc.
The electrode layers of the polymer element are constituted by, for example, carbon particles and an ion conductive resin material (for example, Patent Literature 1).